1. Technical Field
The present invention relates to an organopolysiloxane and to a method for its preparation. More specifically, the present invention relates to an organopolysiloxane comprising monofunctional siloxane units (M unit) and tetrafunctional siloxane units (Q unit) and that also has an epoxy-containing organic group.
2. Prior Art
Various types of MQ organopolysiloxanes are already known in the art. Shirahata in U.S. Pat. No. 4,707,531, issued Nov. 17, 1992, describes a method of making MQ organopolysiloxanes which have long been used as starting materials for varnishes and pressure-sensitive adhesives. According to Shirahata an alkyl silicate is dripped into a mixture of an aqueous hydrochloric acid which contains at least 5 weight percent hydrogen chloride and a trialkylailane or a disiloxine at a temperature of 0.degree. to 90.degree. C.
Shirahata and Fukutani in U.S. Pat. No. 4,946,921, issued Aug. 7, 1990, describe a hydroxyphenyl-containing MQ organopolysiloxane of the general formula ##STR2## where A is a hydroxyphenyl group, R' is an alkylene group having 1 to 4 carbon atoms, n is zero or one, R" is an alkyl group having 1 to 4 carbon atoms, x and z are positive numbers, y is zero or a positive number, x, y, and z have values such that their ratios are 0&lt;(x+y)/z&lt;4, and zero&lt;y/x&lt;5.
Fukutani in U.S. Pat. No. 5,011,901, issued Apr. 30, 1991, describes a chloromethyl-containing MQ organopolysiloxane of the general formula ##STR3## where R' is a monovalent hydrocarbon group having 1 to 6 carbon atoms, R" is a hydrogen atom or a monovalent hydrocarbon group having 1 to 6 carbon atoms, x and z are positive numbers, y is zero or a positive number, and x, y, and z have values such that their ratios are 0.3&lt;(x+y)/z&lt;4 and zero&lt;y/x&lt;100.
However, the groups that may be bonded to the silicon atom in the monofunctional siloxane units (M unit) in the above-referenced MQ organopolysiloxanes are limited to the hydrogen atom, alkyl groups, alkenyl groups, the hydroxyphenyl group, and the chloromethyl group. There have been no reports to date of MQ organopolysiloxane in which the silicon atom of the monofunctional siloxane unit (M unit) carries an epoxy-containing organic group.
The present inventor achieved the present invention as the result of extensive efforts directed at solving the aforementioned problem.